Thermal transport in silver-coated polymer sphere composites by the bidirectional 3ω method

Abstract

The bidirectional 3[Formula: see text] method is an electrothermal technique that is commonly used to obtain the thermal conductivity of materials such as liquids, biological samples, and pastes. In this work, an epoxy-based adhesive was filled with monodisperse 10  μm polymethyl methacrylate spheres coated with silver thin films (AgPS), such that a metallic network that dominated the thermal transport was formed through the composite. The bidirectional 3[Formula: see text] method was used to obtain the thermal conductivity of the conductive adhesive at different volume fractions of AgPS. For 50 vol.% AgPS, corresponding to 3.4 vol.% silver, the thermal conductivity was [Formula: see text] W m−1 K−1. The results show that the thermal conductivity is strongly correlated with the AgPS volume fraction, while maintaining a volume fraction of silver far below the commercial silver paste, which has typical filler fractions of 40 vol.% silver. The results of this work were compared to thermal measurements of the same material by other techniques, and advantages and disadvantages of the methods were finally discussed.